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'[OT]: Hard Drive Crash Recovery. Crowbars'
2002\02\25@211510 by Robert Rolf

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The 'pro' supplies used in high end boxes have serious 'crowbar' SCRs on
their outputs to prevent this sort of thing from happening. When you have $10k
of high performance server/hard drives, you don't worry about $10 of fail-safe
parts.

I suppose you could make up a poor-man's-crowbar with some high wattage
zeners rated at a half volt about the supply values (notably the 5V and 12V rails).
If the supply goes berserk, the zeners clamp and blow the primary fuse.
Wire it up to an old hard drive connector (or Y cable) for easy installation.
Now that you've made me think about it, I'll be doing this tomorrow.

I once has a power supply where the 5V & 12V leads for a drive were reversed.
Brand new SCSI HD and the 'magic smoke' came out the first time I powered it
up. The dealer refused to replace the fried drive since "you should have
checked that the connectors were OK". I certainly check now.  I also highly
UNrecommend them to anyone who asks. In the end they lost a lot more that
the replacement cost of the drive.

A relatively cheap and quick way to do backups is to purchase a second
BIG hard drive in removable drive bay. It is used ONLY for backups.
You pull it out of the system and take it off site once you've done the backup.
With two drives it's even more reliable. You take one home with you, and
bring the alternate in to work the next day (or week).

Robert

Bob Blick wrote:
{Quote hidden}

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2002\02\25@230715 by Bob Blick

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On 25 Feb 2002 at 19:14, Robert Rolf wrote:

> The 'pro' supplies used in high end boxes have serious 'crowbar' SCRs on
> their outputs to prevent this sort of thing from happening. When you have $10k
> of high performance server/hard drives, you don't worry about $10 of fail-safe
> parts.

I've never seen a supply with multiple crowbars. Usually(like this
one) there is a crowbar on the 5v supply, plus a 339 quad
comparator sensing all supplies. The 5 volt line never got too high, it
was the other supplies that did all the damage. That's why the video
card, ethernet card, and floppy drive survived. Everything else was
toast.

Computer was plugged into a UPS, it wasn't a surge, the power
supply just picked a good time to go full duty cycle. Or perhaps the
crowbar somehow triggered, and it forced everything else up as it
tried to restore +5 to the proper voltage?

Redarding expensive power supplies, I'm not convinced they are
any more reliable. When I bought a system with an Athlon, I
followed the recommendation and bought the best power supply I
could, and went so far as to buy ones on the list at AMD. Three
power supplies from two different brands all failed for various
reasons within a few months. I now have a piece of crap power
supply in it and it's been working three years. The expensive power
supplies were heavy, had lots of nice parts in them, but they were
less reliable.

Cheers,

Bob

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2002\02\25@235608 by Robert Rolf

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Bob Blick wrote:
> On 25 Feb 2002 at 19:14, Robert Rolf wrote:
>
> > The 'pro' supplies used in high end boxes have serious 'crowbar' SCRs on
> > their outputs to prevent this sort of thing from happening. When you have $10k
> > of high performance server/hard drives, you don't worry about $10 of fail-safe
> > parts.
>
> I've never seen a supply with multiple crowbars. Usually(like this

The Compaq's I once attempted to service did have multiple crowbars,
as did the DEC PDP 11/xx supplies. Had lots of PDP supplies try to
go AWOL, but the crowbars did their job.

> one) there is a crowbar on the 5v supply, plus a 339 quad
> comparator sensing all supplies. The 5 volt line never got too high, it

If designed correctly, the 339 would have triggered the 5V crowbar and
killed the supply with high loading. Of course a few milliseconds of 50V
isn't going to sit well with 12V parts.

> was the other supplies that did all the damage. That's why the video
> card, ethernet card, and floppy drive survived. Everything else was
> toast.
>
> Computer was plugged into a UPS, it wasn't a surge, the power
> supply just picked a good time to go full duty cycle. Or perhaps the
> crowbar somehow triggered, and it forced everything else up as it
> tried to restore +5 to the proper voltage?

Yes, a lot of supplies use the 5V as a reference for everything else.
Pull it low, but not dead, and it's quite possible the other voltages
would go high enough to pop something. The original IBM PC AT supply had
a low ohm, high watt resistor to load the 12V supply if you didn't
have a hard drive. With the ballast resistor disconnected you got 12V,
and 3V on the 5V line. Brilliant design, NOT!

What does a high power zener cost these days?
Why can't the manufactures charge an extra $5.00 to have a bit
of 'robustness' in a design?

> Redarding expensive power supplies, I'm not convinced they are
> any more reliable. When I bought a system with an Athlon, I

Brand name? With a long warrantee that they'd have to 'make good'
on if their supply failed? Tell us what we should avoid in future.

> followed the recommendation and bought the best power supply I
> could, and went so far as to buy ones on the list at AMD. Three
> power supplies from two different brands all failed for various
> reasons within a few months. I now have a piece of crap power
> supply in it and it's been working three years. The expensive power

Check that the fans are still spinning. Every cheap supply we've had
has lost it's fans after 3-5 years. Of course our machines are on
7x24 since reboots take too darned long.

> supplies were heavy, had lots of nice parts in them, but they were
> less reliable.

That is unfortunate. All it takes is ONE weak component if the design
has intrinsic flaws.

Robert

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2002\02\26@074152 by michael brown

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> What does a high power zener cost these days?
> Why can't the manufactures charge an extra $5.00 to have a bit
> of 'robustness' in a design?

You *are* talking about PC power supplies, correct?  This would be a 50%
price increase in the cost of the supply.  Take a look at these things some
time, most (all?) are not even UL listed, as that would add to the cost too
much.  I can get a new 300watt supply for as low as US$12.00.  I wouldn't
use it in my computer, I'm just saying.

I have seen a good many supplies go bad, but I have never seen one damage
the computer......yet.  Most failures seem to be due to the fan stopping.
It's only a matter of time after that.  ;-)  I've sure seen some melted
parts as they will get a tad warm inside with no fan running.

michael brown

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2002\02\26@194417 by dcchan

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With all these worries about hard-disk crashing, has anybody consider or
even purchase RAID controllers as an insurance. See link
http://www.promise.com

I have no idea about this product...been reading something about
RAID...which stands for "Redundant Array of Indepedent(Inexpensive) Disks"

If what they are selling is what I think it is, then you insert this card
into your PC with a number of hard disks, example 4 hard-disk. If one
hard-disk crashes, then information from the other 3 hard-disk can be used
to regenerate the lost data.

It is also suppose to make the 4 disk look like one large disk (maybe like
total of 3 disks capacity)

It is also suppose to be faster, as data are stored across multiple disk,
and retrival is faster because 3 disks are spinning to get data
simultaneously..

I thought such things are availiable only for HIGH END COMPUTERS, and I am
surprise it is avaliable for PC. Anybody tried this product before ? and Did
I understand what RAID is correctly ?

Derek

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2002\02\26@211155 by Dale Botkin
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On Wed, 27 Feb 2002, Derek Chan wrote:

> If what they are selling is what I think it is, then you insert this card
> into your PC with a number of hard disks, example 4 hard-disk. If one
> hard-disk crashes, then information from the other 3 hard-disk can be used
> to regenerate the lost data.

Correct, assuming RAID 5.

RAID 0 - Striping.  Makes 2 or more disks look like one big drive, no
redundancy.

RAID 1 - Mirroring.  Keeps two copies of the disk on 2 spindles.  Full
reundancy.

RAID 3 & 4 - Forget the details, but they're not commonly used.

RAID 5 - Striping with parity.  A spare spindle is used for parity
information so you can lose one disk (and only one) without losing data.
Requires 3 or more disks.

Then there are combinations - RAID 15 is mirrored RAID 5 sets, etc. for
the truly critical apps & data.

I use RAID 1 mirroring in my Linux machine now.  No special controller
required, the drivers are bult into the OS.  Solaris and most other UNIX
flavors have this as well.

> I thought such things are availiable only for HIGH END COMPUTERS, and I am
> surprise it is avaliable for PC. Anybody tried this product before ? and Did
> I understand what RAID is correctly ?

Yep, you did.  I don't use the Promise controller, but a friend does and
likes it.  Actually he bought the ATA-100 controller and found out there's
one jumper to make it a RAID controller also, same hardware just a
jumper-seleted software feature that saved him some money.  He's tested it
(as I tested my software RAID); works perfectly.  Since they're IDE drives
there's no hot swap capability, but it's not a critical business server,
so no big deal.

I do high end computers for a living - UNIX front end systems manager for
a large online brokerage.  In a critical application we use either
mirroring or RAID 5 - depending on the space needed - then deploy two or
more identical, load balanced servers so if one fails we're still OK.  Of
course there is always the EMC disk arrays...  multiple TB of RAID5 space
that can be dynamically allocated.  Every house should have one!  8-)

Dale

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2002\02\26@220833 by M. Adam Davis

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I use the Promise Fasttrack 66 RAID cards in small stores.  I have two
drives set up in each server as a mirrored configuration, and each night
the server backs up the data to a seperate computer on site.  This gives
2.5 points of failure - if a single HD fails the server keeps chugging
along without a single complaint.  I have to down the server to replace
the bad HD (It supports hot swap, but does not support dynamic
rebuilding - meaning it won't re-mirror a drive while it's in use).

If the server crashed so hard both hard drives are toast then I have the
other on site backup.  The event that all three hard drives are
destroyed at the same time without the store being destroyed as well are
so remote as to not be worried about.  We don't care much about the data
if the store is completely gone (fire, acts of nature, etc), so an off
site backup tips the cost/return on investment scale.

I used one in my personal machine for awhile in a striped configuration
(block one on the first drive, block two on the second, block three on
the first, etc) with two 7200rpm 20GB hard drives, and it performed
noticibly better than another machine with a faster processor that was
using two 10,000rpm scsi hard drives.

They are not considered 'professional', though, and I wouldn't depend on
them completely - ie, keep another reliable backup.  I've never had a
problem with them though, and they've been in place in over 12 stores
for nearly a year now - pretty severe use.

-Adam

Derek Chan wrote:

{Quote hidden}

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2002\02\26@233022 by Mitch Miller

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Something I've not seen discussed on this thread (yet) to consider: Most
data loss is the result of intentional user initiated actions.  While the
data loss is not necessarily intentional, I know so many people who were
just "cleaning up their C: drive" and ended up wiping out entire
subdirectories (including the O/S many times) and were left with nothing.
Even a six figure EMC disk array doesn't protect against that ... there is
simply no substitute for permanent (or at least semi-permanent) backups
which are separate from the live data.  Even having a second hard drive
that you synchronize with nightly leaves this area exposed ... ex: user
deletes file, synchronization process runs nightly for 3-4 days (deleting
file from synchronized media), finally user realizes they deleted file and
want it back.  Seen it too many times.

-- Mitch

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2002\02\27@005242 by dcchan

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I have actually been considering to run down to the computer to purchase the
Promise Card and plug it into my PC. Beside "promise" any other company
making this stuff or any recommendation ?

It sure beat having to make a backup copy once a while wondering when the
disk will fail, because all I need to do it replace the faulty disk, at I am
up and running again without data loss.

Derek

-----Original Message-----
From: pic microcontroller discussion list
[.....PICLISTKILLspamspam.....MITVMA.MIT.EDU]On Behalf Of M. Adam Davis
Sent: Wednesday, February 27, 2002 10:23 AM
To: EraseMEPICLISTspam_OUTspamTakeThisOuTMITVMA.MIT.EDU
Subject: Re: [OT]: Hard Drive Crash Recovery. Crowbars


I use the Promise Fasttrack 66 RAID cards in small stores.

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2002\02\27@033603 by Lee Jones

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> I have actually been considering to run down to the computer to
> purchase the Promise Card and plug it into my PC. Beside "promise"
> any other company making this stuff or any recommendation ?

Adaptec.  IDE versions ATA1200A and ATA2400A (if I recall correctly).
SCSI versions too.

Mylex ExtremeRAID or DAC960 (older models).  I've only used
their products on SCSI drives.

AMD(?) MegaRAID; SCSI.

Dell's PERC SCSI RAID (probably a rebrand).


> It sure beat having to make a backup copy once a while wondering
> when the disk will fail, because all I need to do it replace the
> faulty disk, at I am up and running again without data loss.

RAID is not the same as off-site backups.  It boosts performance
or protects against failure of a single hard disk or both.  To be
able to hot swap drives and rebuild on the fly requires a drive
enclosure/chassis and carriers that support such activities.  It
is frequently easier to buy it built into a server, such as Dell's
Poweredge 1500SC, 2500, etc.

If you want hot swap drive capability in an external enclosure,
check out Dell, Compaq, IBM, and other.  One third party that makes
a nice (though expensive) external enclosure with redundant power
supplies and hot swap is Kingston's Data Silo products.

                                               Lee Jones

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2002\02\27@072255 by Mitch Miller

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On Wed, 27 Feb 2002, Derek Chan wrote:

> I have actually been considering to run down to the computer to purchase the
> Promise Card and plug it into my PC. Beside "promise" any other company
> making this stuff or any recommendation ?

Yeah, 3ware makes some pretty cool stuff.  8 IDE drives in a single PC on
a controller acting as a non-blocking switch.  Allows up to 8 drives to be
concurrently performing ATA requests much the way SCSI works.  Pricey, but
nice!!

-- Mitch

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2002\02\27@073804 by Alan B. Pearce

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>> I have actually been considering to run down to the computer to
>> purchase the Promise Card and plug it into my PC. Beside "promise"
>> any other company making this stuff or any recommendation ?

>Adaptec.  IDE versions ATA1200A and ATA2400A (if I recall correctly).
>SCSI versions too.

I do not know if DPT make ATA versions, but their SCSI cards used to do nice
RAID arrays invisible to the op system.

Also be aware that win NT/2k/XP all have raid built into them. Unfortunately
the workstation/pro version does not do mirror drives but allows striping
which always seemed a backwards way of looking at it. The server versions
allow all useful RAID modes.

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2002\02\27@170737 by Harold M Hallikainen

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       The Tayan motherboard in the machine I'm running on
http://www.hallikainen.org has a Promise RAID controller on the
motherboard. It supports four drives and two modes. I don't remember the
mode numbers, but they allow for drive mirroring or drive striping.
Mirroring gives redundancy by always writing stuff out to two drives.
Striping spreads the data across multiple drives. I believe there is a
striping method that allows recovery on loss of a drive, but this does
not support it. Nonetheless, I am running striping to make it fast and
get a lot of capacity (120 GB on four drives). The controller shows up as
a single SCSI drive to the operating system. Promise has a driver for RH
7.1 Linux that I'm using. The machine boots from this.  They say they are
working on a driver for RH 7.2

Harold



FCC Rules Online at http://hallikainen.com/FccRules
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